The invention relates to gas detectors.
Gas detectors are already known including transducers which respond to the presence of one or more selected gases to change their electrical characteristics to enable, by electrically monitoring such characteristics, the detection of the presence and concentration of the selected gas in an environment. It is usual to provide an instrument having a transducer, an electrical monitoring circuit and a local electrical supply as well as a display for the instrument so that the presence and/or concentration of the selected gas or gases can be readily determined in a chosen environment. Such instruments especially when accuracy is required and low concentrations, a few part per million, are to be measured tend to be expensive and non-robust.
The present invention is concerned with providing gas detectors which are comparatively cheap and are for use in detecting low concentrations of gas particularly carbon monoxide and methane. The gas detectors of the present invention have particular although not exclusive application in detecting the presence of fires or potentially hazardous conditions in underground mine workings.